One known scheme for transmitting and receiving data between communication apparatuses over a network is to, before communication apparatuses perform data transmission via a communication medium (wired/wireless), exchange control signals for reserving a data transmission bandwidth (signaling) between the communication apparatuses and an access controller configured to control access to the communication medium. Examples of schemes using such a transmission procedure include Mobile Worldwide Interoperability for Microwave Access (WiMAX), which is standardized by the Institute of Electrical and Electronics Engineers (IEEE) 802.16e.
FIG. 1 illustrates a signaling procedure for use in Mobile WiMAX, in particular, used in a best-effort service, which is performed after the establishment of a connection between communication apparatuses 100A and an access controller 110 configured to control access to a communication medium, such as another communication apparatus 100B. The communication apparatus 100A includes a processor 101 configured to execute an application or the like, and a communication interface 102. The processor 101 executes an application or the like to generate data, and passes transmission data to the communication interface 102 (at S1). Then, the communication interface 102 transmits a transmission request to the access controller 110 configured to control access to the communication medium (at S2) to request allocation of a bandwidth for transmitting a bandwidth request.
When a bandwidth for transmitting a bandwidth request is allocated by the access controller 110 (at S3), the communication interface 102 transmits a bandwidth request to notify the access controller 110 of a bandwidth necessary to transmit the data (at S4). When the bandwidth necessary to transmit the data is further allocated by the access controller 110 (at S31), the communication interface 102 transmits the data passed from the processor 101 to the communication apparatus 100B (at S5). In Mobile WiMAX, the above sequences have the following correspondences: S1 corresponds to transmission of ranging code, S4 corresponds to requesting a bandwidth using the signaling header, and S3 and S31 correspond to allocation of bandwidths using uplink map (UL-MAP) messages.
The signaling procedure illustrated in FIG. 1 requires times T1, T2, T21, T22, and T23. The time T1 is a waiting time for a frame period of a communication path between the communication interface 102 and the access controller 110. The time T2 is the time from when the access controller 110 processes the transmission request received in step S2 to when the access controller 110 allocates a request transmission slot to the communication apparatus 100A in step S3 in response to the transmission request. The time T21 is the time from receipt of bandwidth allocation in step S3 to transmission using the bandwidth allocated in step S3. The time T22 is the time from when the access controller 110 processes the bandwidth request received in step S4 to when the access controller 110 allocates a message transmission slot to the communication apparatus 100A in step S31 in response to the bandwidth request. The time T23 is the time from receipt of bandwidth allocation in step S31 to transmission using the bandwidth allocated in step S31. There arises a problem in that a delay time T3 including the times T1, T2, T21, T22, and T23 occurs for a period from when the communication interface 102 receives transmission data to when the communication interface 102 transmits the transmission data.
FIG. 2 illustrates an example of a signaling procedure used in a band-guaranteed service, which is performed after the establishment of a connection between communication apparatuses 100A/B and an access controller 110 configured to control access to a communication medium (e.g., communication apparatus 100B). With the use of a band-guaranteed service, a delay time T3 may be shorter than that in FIG. 1.
In the band-guaranteed service illustrated in FIG. 2, the access controller 110 periodically allocates a guaranteed amount of bandwidth (at S3). This may save the times T2 and T22 for the access controller 110 illustrated in FIG. 1 to perform processing, and may also reduce the delay time T3 from when the communication interface 102 of the communication apparatus 100A receives transmission data to when the communication interface 102 transmits the transmission data. However, in a case where the communication interface 102 does not have transmission data, the guaranteed amount of bandwidth is not used (at S6). Such wasteful bandwidth allocation reduces the use efficiency of entire network resources.